Thank you for your questions.
We saw the issues you reported. Unfortunately, the only way to have these strings localized is to override the controls and their CreateChildControls method. This is pretty hard though, since the methods are huge.
That is why we will put these strings in the control template files which you will be able to edit. This will happen in our next 3.6SP3 release, which will come shortly after the RadControls Q2 version (the Q2 should go out in a matter of days as well).
Once you upgrade to SP3, you will be able to localize these strings as well.
We apologize for the inconvenience.
the Telerik team